1. Field of the Invention
The present invention relates to a substrate for a display apparatus, and more particularly, the present invention relates to a substrate for a display apparatus having improved image display quality, including but not limited to an improved viewing angle.
2. Description of the Related Art
In an LCD apparatus that is one of flat panel display (FPD) apparatuses, generally, liquid crystal arrangement varies in response to an electric field applied to the liquid crystal, and thus a light transmittance of the liquid crystal may be changed to display an image.
The LCD apparatus displays the image using the liquid crystal having anisotropy so that the anisotropy of the liquid crystal varies based on a direction of a light that passes through the liquid crystal. The image display quality is dependent on an angle of a viewpoint. In a conventional LCD apparatus, the range of the viewpoint angle is restricted by image display quality deterioration. The viewpoint angle having a contrast ratio of more than about 10:1 is defined as a viewing angle limit/threshold of the LCD apparatus. The contrast ratio is a ratio of a luminance of a dark image to a luminance of a bright image. When the LCD apparatus displays a darker image, and has more uniform luminance, the contrast ratio of the LCD apparatus increases.
The LCD apparatus may include a normally black mode and a black matrix having a decreased reflectivity so as to prevent the leakage of a light and to display the darker image. When voltage is not applied to a common electrode and a pixel electrode of the LCD apparatus having the normally black mode, a black image is displayed. In order to make the luminance uniform, the LCD apparatus includes a compensation film or a liquid crystal layer having a multi-domain. A plurality of domains in the liquid crystal layer forms the multi-domain.
In order to improve the image display quality, liquid crystal molecules may have optimized optical characteristics. In addition, the LCD apparatus may have the multi-domain, a retardation film, etc.
The LCD apparatus of the multi-domain includes a vertical alignment (VA) mode, an in-plane switching (IPS) mode, etc. When an electric field is applied to a liquid crystal layer of the LCD apparatus of the multi-domain, liquid crystal molecules of the liquid crystal layer are aligned in a plurality of directions so that the viewing angle of the LCD apparatus is increased.
A transmissive-reflective LCD apparatus includes a reflection region and a transmission region, and the transmissive-reflective LCD apparatus displays an image having good image display quality in a dark place or a bright place. In general, the liquid crystal layer of the reflection region has different thickness from the liquid crystal layer of the transmission region. The thickness of the liquid crystal layer is determined by a light path. A mobile display apparatus has the VA mode or the liquid crystal layer having the multi-domain to increase the viewing angle.
The transmissive-reflective LCD apparatus includes the retardation film between a polarizer and the liquid crystal layer so that a light that has passed through the polarizer is circularly polarized.
The light transmittance of the liquid crystal layer of the transmissive-reflective LCD apparatus is determined by an angle of the liquid crystal with respect to a vertical direction of the liquid crystal layer so that the transmissive-reflective LCD apparatus may be manufactured without a rubbing process. However, when the transmissive-reflective LCD apparatus is manufactured without the rubbing process, a portion of the liquid crystal layer corresponding to a central portion of the transmission region may be misaligned so that the image display quality of the LCD apparatus is lowered. In particular, a stepped portion is formed at an interface between the reflection region and the transmission region so that a portion of the liquid crystal layer adjacent to the stepped portion is aligned along the interface. In contrast, the portion of the liquid crystal layer corresponding to the central portion of the transmission region may not be aligned along the interface.
When the transmissive-reflective LCD apparatus is manufactured through the rubbing process, manufacturing cost of transmissive-reflective LCD apparatus is increased. In addition, the LCD apparatus may be non-uniformly rubbed so that the image display quality of the LCD apparatus is deteriorated.